The present invention relates to a new automatic liquid flow regulation system, and is used in particular for the automatic control of the flow of a perfusion liquid.
As is known, the injection of a patient with medicinal solutions by perfusion is generally carried out by causing a medicinal solution contained in a bottle to flow directly into the patient's vein through a hypodermic needle in the said vein and connected to the bottle via a flexible tube. The perfusion flow is regulated by means of a hand clamp, and as a result there is:
A lack of precision in th flow regulation, PA1 An instability in the regulation due to mechanical or hydraulic alterations in the flow circuit, PA1 The necessity to monitor the flow.
Flow regulation using a hand clamp consequently does not provide any degree of safety for the patient, who runs the risk either of a closure of the supply tube as a result of an accidental contraction of the clamp associated with the said tube, or a release of the clamp which would result in an inadmissible increase in flow.
Attempts have been made to solve this problem by providing the perfusion systems with a peristaltic pump, but it has been found that a satisfactory control of the liquid flow is not obtained since th peristaltic pumps do not ensure an absolutely regular flow and they only ensure a flow above a certain supply threshold.
An apparatus is also known whose purpose is to rhythmically regulate and monitor the distribution of drops in a perfusion line by means of an electronic circuit which acts on a liquid inflow control system in the perfusion line, wherein the said system consists of a microvalve. Although this ensures that the perfusion system operates safely and can be used satisfactorily, the proposed apparatus according to the prior art nevertheless has the disadvantage that it can only operate with a specific perfusion line comprising a drop counting chamber having particular characteristics and connected to the liquid inflow control microvalve: for this reason this apparatus is not a universal type which can be adapted to all perfusion devices; furthermore, the special structure of the drop counting chamber substantially raises the cost price of the apparatus proposed in accordance with the prior art.
There is known by U.S. Pat. No. 3,252,623 an apparatus for monitoring dispensing of a liquid, and more particularly for controlled intravenous feeding and monitoring of drops of liquid material to humans, which apparatus comprises a photocell which provides an impulse corresponding to each drop to be dispensed, said impulse operating a monostable one output of which operates a bistable; an other impulse generator the power of which is a function of the selected number of drops resets the bistable to zero. The main drawback of such an apparatus resides in the fact that the output impulse of the bistable is compared to the output impulse of another monostable the repetition frequency of which is a function of the selected number of drops.
The object of the present invention is consequently to provide an automatic liquid flow regulation system, and in particular for a perfusion liquid, which satisfies the practical requirements better than the previously known flow regulation systems, more particularly in that it provides a regular and very strict automatic regulation of the liquid flow by means of an accurate and relatively simple and cheap piece of apparatus, thereby eliminating any risk of an inopportune interruption in the flow of perfused liquid, for the patient, or of too rapid a flow of liquid, and also obviating the necessity for constant monitoring of the perfusion system and thus the existence of a large number of staff, wherein the apparatus according to the present invention can furthemore be universally adapted to all liquid flow systems and in particular to commercially available perfusion lines.